Case study: Sedum Green Roof - Kew Green, London

This private project was started at the end of April 2009. A single storey extension on a domestic property was overlooked by both the owner of the building and close neighbours.

The client wanted to achieve an attractive finish as quickly as possible to what was a rather ugly single ply flat roof, but with minimal disruption, due to the restricted access. The client was also concerned about the overall weight of a green roof system, as the extension was a simple structure.

Wallbarn recommended laying an established sedum blanket at least six months old onto a brick-based substrate, with a geotextile separation layer above the Protecto-drain 20P, which would allow free drainage but also hold a certain amount of water within the reservoirs during dry periods.

Wallbarn delivered all drainage components in rolls and the substrate mix in 25kg bags for easy access to the area. The sedum blanket was delivered at the same time on pallets. All layers were installed within 2 working days.

The sedum was specially selected to be colourful and hardy, but also establish itself quickly. It needed to withstand being in semi-shade for large parts of the day.

It was also important that the sedum did not become too thick or aggressive, so the roof-light built into the flat roof would not be obscured in any way.

Within three months what had once been an eyesore……….

…..has become an attractive focal point of the area, doubling the size of garden in a built up area.

Note the difference between this single storey extension and the neighbouring exposed felt roof.

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